This application is based on and claims the priority under 35 U.S.C. xc2xa7119 of German Patent Application 100 00 915.8, filed on Jan. 12, 2000, the entire disclosure of which is incorporated. herein by reference.
The invention relates to a brake for a vehicle and particularly an aircraft, but also a land vehicle, including at least one stator brake disk that is fixed to a rotatable wheel axle, and at least one rotor brake disk that is rotatable relative to the wheel axle and arranged parallel to the stator brake disk. The stator brake disk includes a brake lining or brake pad arranged circumferentially around a supporting ring that is mechanically secured to the wheel axle.
In the field of aircraft construction, it is conventionally known to use hydraulically actuated multi-disk brakes for the landing gear wheels, especially of larger aircraft such as commercial transport aircraft. Such multi-disk brakes include stator disks and rotor disks that are arranged or stacked alternately and parallel to each other to form a brake disk packet. The disks of conventional aircraft brakes are generally made essentially of stainless steel (SST) or carbon fiber-reinforced synthetic composites (CFC). Due to the reduced weight and higher braking power capacity, the brake disks of almost all known military and civil aircraft types of modern construction consist of carbon fiber reinforced composites (CFC). Such CFC aircraft brakes, however, suffer the disadvantage of a high replacement cost, while SST brakes have a relatively short operating life (in comparison to CFC brakes), due to the high loads and resultant wear occurring during the braking of large aircraft.
A typical aircraft brake using CFC material for both the stator and rotor disks is characterized by a lower total weight and a higher braking load capacity in comparison to aircraft brakes of SST material. The CFC brake also avoids the use of an actual brake pad or brake lining per se, because the braking effect is achieved by means of a so-called disk/disk pair.
On the other hand, a typical aircraft brake using SST material is constructed as a multi-disk brake packet including stator disks and rotor disks arranged alternately in sequence one after another on the wheel axis, and received between an end disk (or backing disk) and a pressure disk (or pressure plate). The end disk is located on the side of a counter support bearing, which presses or braces against a support member that is rigidly mounted on the wheel axis and, for example, rigidly screwed to the landing gear strut or the like of the aircraft landing gear. The pressure disk, on the other hand, is located on the side of a braking piston housing which is screwed to the support on the wheel axis. A braking piston received in the braking piston housing selectively exerts a braking force onto the pressure disk in a direction toward the counter bearing, so as to press the alternately stacked discs into frictional contact with each other.
The brake linings or pads, which are subjected to extreme loads and resultant high wear due to the braking process, are rather difficult to replace, i.e. exchange, after they have been worn beyond an acceptable limit. Namely, a complete disassembling of the brake arrangement is practically always required when it is necessary to exchange the brake linings or pads. Since the brake pads are secured to the brake disk or rotor support ring by rivets, these rivet connections must be bored out or otherwise broken or released in order to exchange the used brake pads with new brake pads. Then the new brake pads are once again riveted onto the associated support ring. Then, the rest of the previously disassembled brake arrangement must be reassembled. As can be appreciated, this is a very time consuming and costly process. Also, the support ring can suffer wear or damage as a result of repeated removal of old rivets and re-setting of new rivets. The overall maintenance cost and effort is quite considerable for aircraft using such brakes, because such civil aircraft operated by commercial airlines have rather strictly limited time frames prescribed for the maintenance and replacement of the brakes and particularly the brake pads.
The German Patent Publication DE 197 11 829 C1 discloses a method of manufacturing a fiber-reinforced composite ceramic material with high-temperature high-strength fibers on the basis of silicon, carbon, boron, nitrogen or compounds thereof, which are reaction bonded with a matrix of silicon or silicon alloys or compounds. Such fiber-reinforced composite ceramic materials are also usable for manufacturing brake disks in a simple and economical manner. Other ceramic materials are also generally known in the art. For example, a fiber-reinforced ceramic with an oxide system, for example Nextel(trademark), fibers of the 3M Company, based on alumina with an oxide matrix, such as mullite for example, or in combination with a carbide matrix, such as silicon carbide for example, are generally known in the art.
Without further going into the details, there is no known reference in the relevant trade literature, that makes a suggestion to use brake pads made of the above mentioned materials in the above mentioned manner for vehicle brakes and particularly aircraft brakes. The trade literature further gives no hints or suggestions toward the particular localized use of at least one of such brake disks as a stator or a rotor within a multi-disk brake packet of an aircraft brake.
In the field of aircraft construction, there has been a constant effort to achieve landing gear wheel brakes having a relatively low weight, a relatively high braking power capacity, an economical fabrication, and relatively low expected maintenance and replacement part costs, in comparison to prior conventional aircraft brakes. Mostly due to these constant efforts to achieve these advantages in combination, there has never been achieved or suggested a multi-disk brake with alternating disks of different materials, and particularly using a fiber reinforced ceramic for one of the two brake disks that will come into contact with each other, in view of the braking properties and the unavoidable wear of the effective brake surfaces of such a vehicle brake.
In view of the above, it is an object of the invention to provide a vehicle brake arrangement having a low total weight and a high braking power capacity, and which utilizes brake disks that achieve a simple and economical maintenance with a simple and quick exchange of the brake linings or pads, in comparison to prior art brake arrangements. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as apparent from the present specification.
The above objects have been achieved according to the invention in a vehicle brake arrangement including a rotatable wheel axle, and a brake disk stack or packet that includes at least one stat or brake disk secured on the wheel axle, and at least one rotor brake disk that is rotatably supported relative to the wheel axle and is arranged parallel to the stator brake disk. The stator brake disk includes a support arrangement that is mechanically connected to the wheel axle and a brake pad arrangement secured to the support arrangement. The support arrangement includes a support ring and a plurality of support members or support arms that protrude substantially radially from the outer circumference of the support ring and are circumferentially spaced apart from one another. The brake pad or lining arrangement includes a plurality of plate-shaped brake segments that are respectively removably and exchangeably arranged between respective neighboring ones of the support arms.
Throughout this specification, the term xe2x80x9cplate-shapedxe2x80x9d is intended to designate a shape of a member that extends along a plan and that is significantly larger in two dimensions along that plane than in a thickness dimension perpendicular to that plane. Throughout this specification, the terms xe2x80x9cradialxe2x80x9d, xe2x80x9ccircumferentialxe2x80x9d, xe2x80x9caxialxe2x80x9d and the like are to be understood with respect to the rotation axis of the rotating set of brake discs, unless otherwise stated or apparent from a particular context.
The above objects have further been achieved according to the invention in a vehicle brake arrangement including at least one stator brake disk and at least one rotor brake disk as generally described above, whereby the stator brake disk includes a support arrangement and a brake pad arrangement secured thereon. The brake pad arrangement includes a plurality of brake segment pads made of a sintered metal material and adhered onto a plate-shaped brake segment carrier, whereby the brake segment carrier and brake segment pad together form a respective brake segment which is removably and exchangeably arranged on the support arrangement. The rotor brake disk is made of a ceramic material. By selectively bringing the rotor brake disk into contact with the brake segment pad of the stator brake disk, the resulting friction provides the desired braking effect.